Actually not. They had more than sufficient grounds to fire Churchill long since, if they really wanted to.
If you did away with the tenure system, the results are entirely predictable. The leftist scum who control the levers of power at most universities would promptly fire all the remaining conservatives and decent teachers.
As it is now, a conservative professor is merely required to keep a low profile and keep his opinions to himself for maybe fifteen years, while he gets through college, graduate school, and tenure.
Then if there's anything still left inside his head after that long hibernation, he can start to say what he thinks--although he will suffer for it at salary and promotion time.
Do away with tenure and there would be no one left in academia but the politically correct morons who are currently running things.
How did the filthy dogs get and keep the power in the first place? Do away with tenure and the agendas will be up front as there will be a continuing dog fight about teaching positions. Schools will separate according to ideology, as they probably should, and let the market decide.